The present invention relates to a method and apparatus for continuously casting of metal in horizontal direction.
The technique of continuously casting metal in horizontal direction comprises the step of causing the molten metal to flow continuously from a container of refractory material through an opening in the side wall thereof into a cooled ingot mold open at opposite ends and arranged in horizontal direction, and to withdraw the partially solidified product produced in the ingot mold from the latter. The process of progressive solidification of the product in the interior of the ingot mold is known so that the manner of extraction of the product as well as the manner of function and construction of the ingot mold constitute aspects of the technique in question which may be considered as well mastered, and for which various satisfactory solutions have already been proposed.
However, this is not the case as far as the flow of the molten metal from the container towards the ingot mold is concerned. To obtain a satisfactory flow of the metal poses a technological problem in realizing an effective joint between the container of refractory material and the cooled ingot mold. It has been ascertained that the metal has a tendency to start solidification not in the ingot mold, but already in the region of the joint or connection between the container and the ingot mold, which phenomenon causes the metal to stick to the joint, and leads to a tearing or renting of the solidified portion, provoked by the traction imparted to the product to withdraw the latter from the ingot mold. This causes considerable difficulties in the casting process and such tearing will result into considerable surface defects in the cast product, in fact, the defects may create openings upstream of the ingot mold causing thereby a complete emptying of the metal from the container or refractory material. In addition, the aforementioned sticking of the metal causes a progressive deterioration of the joint, which, in turn, contributes to an amplification of the above-mentioned phenomenon and will lead almost unavoidably to a stopping of the casting operation, the faster, the higher the temperature of the molten metal is. It is for this reason that the technique of continuously casting metal, especially steel, in horizontal direction is at the present time not generally used, and this despite notable perfections with regard to the joints used, as well as with regard to the choice of material which form the joint.
Various propositions have already been made to resolve the above-mentioned problem of passing of molten metal from a container of refractory material into a horizontally extending ingot mold. For instance, the U.S. Pat. No. 3,630,266 describes a method of continuously casting metal in horizontal direction according to which a stream of molten metal is caused to flow through a conduit of refractory material into a cooled ingot mold having an inner cross section superior to the cross section of the conduit of refractory material, and in which a fluid under pressure is injected into the space between the external periphery of the conduit of refractory material and the internal surface of the adjacent ingot mold in such a manner to press the molten metal out of the aforementioned space. This arrangement aims to substitute a fluid joint for a solid joint which can be continuously renewed. More specifically, the arrangement disclosed in the aforementioned patent constitutes a way to put into practice an improvement in fluid joints, to be used in a method and apparatus of continuously casting metal in horizontal direction. The molten metal flows directly from the conduit of refractory material into the ingot mold by forming a meniscus in such a manner that the start of the solidification of the metal in the ingot mold can in no way lead to a deterioration of the extremity of the conduit of refractory material. The arrangement to put into practice the aforementioned method has therefore the characteristic that the conduit of refractory material is not in material contact with the ingot mold.
Considering the substantial vertical disposition of the aforementioned meniscus, it will follow that the essential uniform pressure of the fluid will be opposed to the ferrostatic pressure, the value of which will linearly increase with the height of the interface between fluid and the liquid metal. This will lead to a certain instability of the geometry of the meniscus, which instability will only be partially diminished by the existence of surface tensions. Due to this instability, the molten metal is liable to penetrate, for moments, in the space located between the extremity of the conduit refractory material and the adjacent wall of the ingot mold and solidify there, which will lead to the tearing of the solidifying metal mentioned above and which, in addition, may occasion a piercing at the level of the fluid joint, so that the latter will not be able any longer to function satisfactorily.